This study addresses the provocative question: Why don't more people alter behaviors known to increase cancer risk? (PQ4). Emerging work in behavioral economics has shed light on the critical role of reward-based decision-making processes in health risk behavior. In parallel, research in cognitive neuroscience has clarified the central role of the dorsolateral prefrontal cortices (DLPFC) in cognitive control during decision-making. Thus, we propose to integrate these lines of research and advance the science of behavior change by testing whether enhancement of DLPFC function via neurocognitive training improves decision-making processes that contribute to risk behavior. Young adults (ages 18-30; n=150) will participate in a five-week web-based neurocognitive training program or a cognitive stimulation (control) condition, based on random assignment. The evidence-based neurocognitive training focuses on enhancement of targeted cognitive processes to facilitate self-control and goal-directed behavior: sustained attention, working memory, and response inhibition. This intervention, shown to be highly effective for cognitive remediation in neuropsychiatric illness, has been adapted as a web-based tool for the proposed study to enhance cognitive function in healthy subjects. Importantly, our pilot data support the feasibility, high levels of compliance, and beneficial effects on neurocognitive performance. Our primary aim is to evaluate effects of neurocognitive training on neural activity and decision-making behavior. Our secondary aim is to examine the neurobehavioral mechanisms that mediate effects of neurocognitive training, including changes in executive cognitive function. Changes in decision-making processes and neural activity associated with neurocognitive training will be assessed at baseline and post-training by acquiring functional magnetic resonance imaging (fMRI) while participants perform reward-based decision-making tasks, specifically delay discounting and risk sensitivity. Cognitive performance will be assessed at these time points using a validated battery of tasks, in order to examine mediation effects. A three-month follow-up assessment will test the durability of the effects of neurocognitive training beyond the training period. Thus, this application breaks new scientific ground by applying novel concepts and tools from the field of cognitive neuroscience to accelerate the study of basic mechanisms of behavior change. These data will inform the development of novel and more comprehensive interventions for behavior change (e.g., combining neurocognitive training with existing behavioral interventions). As a basic mechanism study, the knowledge generated will be relevant to multiple health risk behaviors, enabling a potentially broad impact on cancer prevention.